Embodiments of the present disclosure relate to an array substrate and a liquid crystal display (LCD) device.
Liquid crystal display devices are common flat display devices at present, and thin film transistor liquid crystal display (TFT-LCD) devices are the popular kind of liquid crystal display devices in the market.
LCDs can be divided into types based on the form of driving electric field. FIG. 1A is a schematic diagram showing a configuration of pixel units in a conventional fringe-field switching (FFS) type TFT-LCD. As shown in FIG. 1A, the array substrate of the FFS type TFT-LCD can comprise a base substrate (not shown). Data lines 5 and gate lines 2, which are orthogonal to each other to define a plurality of pixel units, are formed in a pixel region (display region) in the central portion of the base substrate. Each of the pixel units may comprise a switching element TFT, a pixel electrode 11 and a common electrode 13, and the pixel electrode 11 and the common electrode 13 may be formed of transparent conductive materials such as indium tin oxide (ITO) or indium zinc oxide (IZO). The common electrode 13 is disposed in the entire region of the pixel unit, with a plurality of slits arranged regularly in parallel with the data line 5. During manufacturing of the array substrate, the pixel electrode 11 can be formed before the common electrode 13. The pixel electrode 11 is disposed in the entire region beside the gate line 2 and the data line 5 corresponding to the pixel unit, and is separated from the gate line 2 and the data line 5 by a distance. The pixel electrode 11 and the common electrode 13 are isolated by using a transparent insulation material. The switching element TFT can comprise a gate electrode 3, an active layer 6, a source electrode 7 and a drain electrode 8, and may be placed at a position where the gate line 2 intersects the data line 5. The drain electrode 8 and the pixel electrode 11 can be connected by via holes or directly; as shown in FIG. 1A, they are connected directly. The carrier migration between the source electrode 7 and the drain electrode 8 is controlled by the gate electrode 3 connected to the gate line 2. The liquid crystal molecules can be rotated by driving of the potential difference produced between the pixel electrode 11 and the common electrode 13. Then the transmittance of the liquid crystal cell can be controlled by a variety of potential differences so as to form different levels and thus realize displaying.
FIG. 1B is a schematic diagram showing an orientation state of the liquid crystal molecules in the conventional FFS type LCD. As shown in FIGS. 1B and 1A, during the driving operation, the liquid crystal molecules 20 in the liquid crystal cell are arranged in a vertical direction as shown in FIG. 1A when no electrical field is applied across the substrates; and the liquid crystal molecules 20 in the liquid crystal cell are arranged in a horizontal direction as shown in FIG. 1B after an electrical field is applied. Since the liquid crystal molecules in the liquid crystal cell are rotated in the same direction after the electrical field is applied, and the refraction index of the liquid crystal molecules is anisotropic, the liquid crystal display device is in different displaying states at different viewing angles, and the displayed colors at different viewing angles are also different, resulting in “color shifting.”
A pixel configuration is proposed in order to reduce “color shifting”, as shown in FIG. 1C, which is a schematic diagram showing another conventional pixel configuration. The gate electrode 3, the active layer 6, the source electrode 7, the drain electrode 8 and the pixel electrode 11 are similar to those shown in FIG. 1A, but the common electrode 13 has a configuration different from that shown in FIG. 1A. The common electrode 13 shown in FIG. 1C has curved slits in the horizontal direction, and a long-side midline of the slits is parallel to the gate line 2, with the curved point of the slits as a boundary line. Since the electrical field on both sides of the boundary line at the curved portion is symmetrical about the boundary line during the driving process and the crystal liquid molecules 20 are rotated in two directions opposite to each other, which are symmetrical about the boundary line, it is possible to realize self-compensation so that “color shifting” can be reduced to a certain extent.
However, in the pixel configuration shown in FIG. 1C, there are slits having a shape different from those of the curved slits or regions or no slit at the edge regions, such as the lower portion, the upper portion or the like. The electrical field produced in those regions is different from that produced in the regularly shaped slits, resulting in the liquid crystal molecules being rotated differently. As a result, the displaying effect of the entire pixel is affected disadvantageously, thus it is necessary to enlarge the area of the black matrix (BM) on the color filter substrate for shielding such regions. The aperture ratio and the transmittance of the liquid crystal cell are decreased and then the display contrast ratio is affected.